In a response to environmental concerns and new regulations on refrigerant compositions used in the refrigeration and air conditioning industry, new refrigerant compositions are being developed. The environmental friendliness of refrigerants is often characterized by one or both of a criteria known as “global warming potential” (GWP), or a criteria known as “ozone depletion potential” (ODP).
The GWP value is a number established by the Intergovernmental Panel on Climate Change (IPCC) that refers to the amount of global warming caused by a substance. The ODP value is a number defined by the United States Environmental Protection Agency that refers to the amount of ozone depletion caused by a substance as compared to chlorofluorocarbon-11 (CFC0911, chemically known as trichlorofluoromethane), as given in 42 U.S.C. 7671, “(10) Ozone-Depletion Potential”, incorporated by reference.
By way of illustration of the progress made thus far, the quest for more environmentally friendly refrigerants was pursued in earnest in the 1980's in response to theories about the depletion of atmospheric ozone due in part to refrigerants such as R-12 (dichlorodifluoromethane), which has a GWP of about 1600 and an ODP of 1. In the 1990's, refrigerants having lower ozone depletion potential, such as R-134a (1,1,1,2-Tetrafluoroethane, also called tetrafluoroethane), were introduced. R-134a has an ODP of zero, but still has a GWP of about 1200.
In many cases, a new refrigerant material, besides having low impact on the environment, should also have one or more of the following characteristics: capability of functioning in many existing refrigerant systems, relatively low flammability, relatively low toxicity, have minimal or no reaction (e.g. corrosion) with aluminum, copper and iron at temperatures below 175° C., or good thermal stability as tested using ANSI ASHRAE 97.
Leck et al. (WO 2007/126760) teaches the use of stabilizers including silanes in compositions containing an iodotrifluoromethane refrigerant. Mouli et al. (WO 2008/027595) teaches the use of alkyl silanes as a stabilizer in refrigerant compositions containing fluoroolefins. Phosphates, phosphites, epoxides, and phenolic additives also have been employed in certain refrigerant compositions. These are described for example by Kaneko (U.S. patent application Ser. No. 11/575,256, published as 20070290164) and Singh et al. (U.S. patent application Ser. No. 11/250,219, published as 20060116310). All of these forementioned applications are expressly incorporated herein by reference.
Certain compositions (see for example Leck et al. U.S. patent application Ser. No. 11/653,125 Publication No. 2007/0187639, paragraph 10, hereby incorporated by reference) having a low ozone depletion potential and a low GWP have been proposed for use in a refrigerant composition.
Polymeric materials such as a fluoralkyl polysiloxane (see for example Kawaguchi et al. U.S. Pat. No. 6,475,405, column 9, line 13) have been proposed or used as an anti-load additive in a refrigerant composition.
Polysiloxane polyoxyalkylene block copolymers have been used as a surfactant with fluorocarbon foam blowing agents by Singh et al. (WO 2006/069362) who teach foaming of polymers using the fluorocarbon/surfactant composition.
There are continuing efforts to develop improved refrigerant compositions having improved properties such as relatively low environmental impact, relatively good compatibility, relatively low corrosivity to metals, relatively low cost, relatively low acid number, any combination thereof, and the like. Improvements in one or more property of the refrigerant composition typically negatively affect one or more different properties.
Accordingly there is a need for a robust acid scavenger for use in refrigerant compositions that can economically and efficiently provide one, two, three or more improved properties. In particular, there continues to exist a need for improved acid scavengers in refrigerant compositions having a low global warming potential, a low ozone depletion potential, or both.